Since I'm a newbie myself, and had quite a bit of trouble modifying the IMP portraits, I want to add -for the convenience of other NOOBs- that the IMP .sti's are not at 51-56, but from 200 through 215. For me, modifying 51-56 sti's did nothing in the game (or nothing I noticed on superficial scanning, anyway). Maybe I did it wrong, but changing 200-215 did the job alright. What I did was extracting the .slf into BIGFACES, then scanning for the proper image I used in the game, changing said image, bingo. You can delete the extracted BIGFACES afterwards, too, to speed up loading time; I did it just to find the respective numbers of the original IMP portraits.